There is evidence for enhanced total X-ray luminosities per unit of
star formation rate (\(L_{\rm X}\) /SFR) and high-mass X-ray binary
(HMXB) populations in extremely metal-poor galaxies (Z/Z\(_{\odot }\)  \(<\) 
0.1) compared to those of \(\sim \) Z\(_{\odot }\) 
[1]}, [2]}, [3]}, [4]}, [5]}. Furthermore, examples of
nearby Heii nebulae associated with HMXBs that appear to act as
the only ionizing source are reported
[6]}, [7]}, [8]}. Thus HMXBs have been proposed as
one of the leading mechanisms to ionize He\(^{+}\)  in SF systems.
However, it has been recently questioned whether they can provide the
required He\(^+\)  ionizing flux [9]}, [10]}, [11]}.
Variability of the X-ray source could alleviate this conflict, but so
far only the extensive study of the puzzling Heii\(\lambda \) 4686-emitting nebula N44C in the LMC considered the
effects of an on-off switching X-ray source in time periods of years
[12]}.
